In the foreground of the nuclear talks between Iran and Western powers that got under way in Geneva this month were centrifuges, yellowcake and enriched uranium — all elements of what Iran calls a peaceful nuclear-energy program and what the West worries is a route to a nuclear weapon. But Iran has also charted a second route, one that could produce fuel for a possible bomb not from highly enriched uranium but out of plutonium, a product of the heavy-water reactor nearing completion in the hills outside the city of Arak, 300 km (190 miles) southwest of Tehran. Heavy water is water with an extra neutron, useful in moderating a nuclear reaction.

Because it is not yet up and running, the Arak heavy-water reactor has remained in the background of the nuclear controversy. But it looms larger every day. The reason: once Arak goes online, the option of destroying Iran’s nuclear program with air strikes becomes moot. The reactor is essentially invulnerable to military attack, because bombing one risks a catastrophic release of radioactivity. In the words of Israel’s last chief of military intelligence, Amos Yadlin, who piloted one of the F-16A’s that cratered Iraq’s Osirak heavy-water reactor in 1981 before it was due to become operational: “Whoever considers attacking an active reactor is willing to invite another Chernobyl, and no one wants to do that.”

That reality is the reason why some experts are drawing attention to a peculiar notice filed by Iran’s nuclear agency to the International Atomic Energy Agency (IAEA) in May. Iran told the U.N. agency that, as it readies the Arak plant for operation, it intends to do a practice run: instead of inserting real fuel rods filled with uranium into the reactor’s core, where nuclear fission occurs, they would insert inert “dummy” fuel rods. And instead of pumping heavy water into the reactor to moderate the nuclear reaction and absorb the thermal energy being released, Iran said it plans to use “light water,” just ordinary H2O.

The plan mystifies experts, who take particular issue with testing the system using light water. The facility would be contaminated by ordinary H2O, which if mixed with heavy water would render the latter unusable, because in order to work heavy water must be 99.75% pure.

“Anything above that is hard to achieve and testing the system with light water would leave a residual atmosphere of H2O that would degrade the heavy water when it is added,” writes one U.S. specialist of heavy-water reactors, who has worked with the Institute for Science and International Security (ISIS), a Washington, D.C.–based think tank, and who shared his assessment on condition he not be identified further. In other words, rather than save time, using ordinary water would delay the project for the weeks required to clean the system thoroughly enough to assure no trace of H2O remained; it wouldn’t take much to dilute the heavy water below 99.75%.

Iran’s stated intentions are unlikely enough that an Israeli nuclear specialist suggests that they might be a ruse. Ephraim Asculai, a scientist retired from the Israel Atomic Energy Commission, warns that Iran may have no intention of carrying out a dry run at all. It may be a cover story, he posits, for a plan to rush the installation of live fuel rods and heavy water instead — essentially getting the Arak facility “hot” before the outside world expects, at which point it becomes invulnerable to military attack. There might then be no way to stop Iran’s nuclear program short of invasion.

“At that point, they are in the ‘zone of immunity’ as it’s called,” says Asculai, who has also worked at ISIS; he is currently a senior research fellow at the Institute for National Security Studies, a think tank at Tel Aviv University.

Although Iran already has enough enriched uranium to fuel more than one bomb — should it make the decision to convert the enriched uranium to military use — that’s not all the world must worry about. “The Arak reactor is increasingly relevant and, yes, it’s been a sideshow,” says Mark Fitzpatrick, a former State Department nonproliferation chief now at the London-based International Institute for Strategic Studies, or IISS, where Asculai laid out the “ruse” possibility during a September talk. “The angle of Iran pulling a fast one isn’t something that can be dismissed,” says Fitzpatrick. “I think it’s unlikely,” he adds — because so rash an act would run counter to Iran’s patient behavior to date and it would take “a couple of years” to generate enough plutonium for a bomb. “But it’s something that should be factored into whatever is tabled in Geneva.”

U.S. officials say Arak is indeed on their radar. “We have very serious concerns about them having a plutonium capability, another pathway for fissile material for nuclear weapons,” a senior American official told reporters before the first round of talks since the election of Iranian President Hassan Rouhani; a second round is set for early November. “It is a subject,” the senior official said, “of enormous concern.”

That concern is shared by other Western nuclear experts who worry that Iran might try to sneak the plant online. Olli Heinonen, a former IAEA deputy director who is now at Harvard University’s Belfer Center for Science and International Affairs, says Iran might rush to declare the Arak plant operational before a watching world thinks it has produced enough fuel rods necessary to power the plant, which outside experts estimate at 100 to 150. Manufacture of the rods has apparently lagged, but Heinonen says Iran might install a far smaller number of fuel rods, perhaps as few as the 10 currently known to be in hand, and with that announce that Arak had become operational, and therefore too dangerous to bomb.

“It might be an exaggeration, but they could try to assert that the reactor is now loaded,” says ISIS president David Albright. Albright says that, technically, an Iranian claim that the reactor was “operating” with just 10 or 20 fuel rods would amount to a bluff, because more fuel would have to be in place to make the plant invulnerable to bombing. “Even if the fuel is partly loaded, the reactor could still be destroyed, and the radiological consequences of that would be very slight, if any,” he says. All that, of course, assumes that outsiders had a high level of confidence in how many rods are installed.

Iran claims the Arak plant is intended to produce isotopes for a variety of medical uses. But the reactor is far larger than required for that purpose, and, if fully operational, would generate enough plutonium to fuel two nuclear weapons annually. Extracting the plutonium would require another step, including the addition of a reprocessing facility Iran has not yet built, “but it wouldn’t be beyond them to get it on the black market, or more likely, from North Korea,” Fitzpatrick says.

Albright suggests another possibility, one altogether more heartening for the West: that the Iranians’ plan to test the plant with light water is sincere. “It’s not very smart,” he says, “which maybe implies something about Iranian capabilities and worries about the reactor.” The plant is years behind schedule, and the timetable slipped again after Iran’s May statement to the IAEA. The plan then was for a dry run in the final three months of 2013 and for the reactor to come online early in 2014. The timeline has been pushed back, but no one knows how far. IAEA inspectors complain that Iran has held back design information and limited their access to parts of the site.

“Before the delay was known, I estimated they could produce a plutonium device sometime toward the end of 2016, if everything went well for them,” says Asculai. “So there is still time. And meanwhile,” he says, “the enriched uranium route is really there.”

Karl Vick has been TIME's Jerusalem bureau chief since 2010, covering Israel,the Palestine territories and nearby sovereignties. He worked 16 years at the Washington Post in Nairobi, Istanbul, Baghdad, Los Angeles and Rockville, MD.

The problem is not Iran. The problem is the radical, Islamic dictatorship that controls Iran. The Ayatollahs brutally oppress the Persian people, are the major sponsor of terrorism in the Middle East and around the world, and are racing to acquire nuclear weapons in order to intimidate and possibly incinerate other nations. If ever there was a need for regime change, it's now.

Iran has learned from North Korea: an atomic superpower and heavily armed army/government will avoid a foreign (U.S.A.) invasion. The only hope to get rid of the mullahs is from the inside; they are crazy enough to use all the weapons at their disposal in any scenario (both Iran and North Korea) and have vast experience eliminating opposition in their countries and even abroad (Syria's case).

Quote, quoting you .. If Iran gets the bomb it is hard , if not impossible, to see how a nuclear exchange between Iran and Israel could be avoided" Close quote

Now you know the answer to that . The Soviet Union had the bomb and we had the bomb and we sat facing each other for four and a half decades and did not engage in a nuclear exchange.

Norman Podhoretz:

I will give you Bernard Lewis's answer to that question and than I will give you my own. Bernard Lewis points out that deterrence worked with the Soviets and the Chinese because the Soviets were not suicidal and they knew that if they launched a first strike there would be a second strike tha which would annihilate them --- mutual assured destruction

Peter Robinson:

And it worked

Norman Podhoretz

Mutual Assured Destruction can't work in relation to Iran because these are people who are in love with death

Bernard Lewis:

For them it is not a deterrent, it is an inducement

Peter Robinson:

Truly? Truly?

Norman Podhoretz:

Now I will give you my answer to this. That's' Bernard's answer to the question My answer to the question is to imagine a scenario which most people are horrified . I've tried this all the time , people shy away from it. Imagine that Iran gets the bomb. OK and the Israelis are siting there and asking themselves, do we wait for them to hit us and then retaliate out of the rubble or do we preempt it first? The Iranians are asking themselves the same question. Do we wait for the Israelis to hit us or do we hit them first . We've never had a hair trigger situation like that since the invention of nuclear weapons . If you just imagine the rulers of Iran asking themselves that question . Somebody is gonna beat the other to the punch . And I can't see that unstable situation lasting for very long, maybe even as along as a few weeks or months

Mr. Vick - please recognize that the "come-on" headline of "If Iran Can Get This Reactor Online, It May Be Invulnerable to Military Attack" is substantively DIFFERENT than the actual headline of "If Iran Can Get This Reactor Online, Israel May Not Be Able to Bomb It".

If editors or other personnel made these changes instead of you, please route this comment to them.

Summary: carelessness with words = decrease in credibility with readers.

Is it me, or does the Fairness Act-less Media seemingly stop at nothing until the United States is duped into a series of fiscally imprudent, purportedly "necessary" Military missions against (ahem) UN Sanctioned states? We are the United States.

We can flatten and destroy any REAL threat to the People as King Augustus the Strong would a pewter plate.

"then eliminate super-PACs designed to lull Congress into making America a weak and listless debtor State."

As usual, the mere mention of Israel brings out all the mad dogs barking
and attacking their keyboards with holy fervor. Somehow they believe they can
convince the world that a nuclear Iran is nothing to worry about. They'll keep
at that even while one Arab country after the other will succumb to Iranian
nuclear blackmail, and the more resourceful ones respond with nuclear arms
programs of their own. Can you envision a Middle-East where the Asads, the
Muslim Brotherhoods, the Ayatullas, the Wahabis, and any other fanatic is
wielding nuclear weapons and breeding 9/11 type Jihadists? Can you extrapolate from past use of chemical weapons in these hands? Just imagine the headlines: Half a Million civilians perish as Asad's loyal forces bomb Aleppo; "I didn't authorize the use of Atom bomb", says Asad. "It must be a rebels provocation"... No UN personnel is allowed into the radiation zone where Iranian nuclear experts conduct evidence mitigation operation.... Iran demand invitation to become a permanent member of the Security Council. Turkey put its armed forces on red alert... Erdugan: "we purchased knowhow and manufacturing facilities from Pakistan...to counter the technology Syria gets from North Korea... Price of crude goes over 200 USD/bl as Saudi Arabia heeds Iranian demands to limit production... China secures an exclusive deal with Iran. European tankers are not allowed into the Gulf...

Man, all the left-wing loonies have gathered here. Vick is no friend of Israel. He has written some very unfair and disparaging articles, omitting of course to say anything equally critical of the Palestinians, whose stubbornness and maximalist demands have successfully torpedoed every single attempt at making peace. As for Iran, there are some good ones here. "None of what Iran has done is illegal"? Ignoramus maximus. Ever heard of the half-dozen Security Council resolutions (contrary to General Assembly ones, the SC ones are compulsory) that Iran has blithely ignored? All their lies and dissimulations over the last 20 years? That counts for nothing for the professional israel haters here, of course. And let's not forget the usual trope that Israel must relinquish its nuclear weapons (even though it's never threatened anyone as they are strictly for defensive purposes), but if they abandon them, that will induce Iran to do the same? How many loonies have escaped from the asylum? I ask again: why have they all gathered here? Have they been chased from everywhere else?

In this article, Mr. Vick relies on information provided by Mr. Albright and other so called "scientists: from ISIS. Both Mr. Albright and ISIS are known agents of Mossad, and tasked with blending small facts with large lies for manipulating public opinion. These fabrications which are then quoted in this article, become facts for our AIPAC bought and paid for Congress, which in turn direct American foreign policy.

Let's not forget that Mr. Albright was the so called "Scientist" who pushed for Iraq war and discovery of Saddam's non-existant nuclear weapons. Enough blood and treasure for these phony scientist who are at the service of foreign governments.

The 'West' isn't entirely convinced that what Israel claims about Iran and its nuclear intentions, isn't a very large figment of a hyperactive imagination at best and pure horse pellets on a good day.

One of the remarkable products of a reactor (along with them 'nukuler weapons' and ignored in this piece) is heat ... a lot of heat. Most reactors produce steam heat to turn the turbines used to produce electricity, which then can be converted to other forms of energy. You can hide an atomic reactor under a mountain but you still need a method of dissipating that heat. It can't be buried under the mountain, and so it is a potential target. No heat dissipation, no reaction, no operating reactor, no nukes ... or anything else.

But we all know this isn't about reactors, it's about getting somebody to bomb Iran. Or to back-up the Israelis who claim they really, really, really need to bomb Iran ... for humanity's sake even.

How about, for humanity's sake, Israel leads the movement to a nuclear-free zone in the middle east? How about Israel solves its ''Palestinian problem'?

And how about Time stops publishing Israeli crap to give it 'credibility' it wouldn't get anywhere else?

It's not going to help them. We spend a Bagillion Kagillion dollars a year on our military and we can walk into their country at any given point in time and do as we please. That's one small perk of being the most powerful country in the world.

Mr karl vick, why you keep on demonizing and putting the fright in the world about Iran? Why don't you dedicate one, only one analysis, to the illegal behaviour of your bosses in Israel? Why Israel has never integrate the watch dogs of WMD? Everybody in the world knows that Israel has a big stockpile of chemical and nuclear weapons? Has Israel ever accepted this fact? Now, if you compare the behavior of these two countries, Israel and Iran, with respect to keeping the peace, you will see that the most dangerous for the peace in that part of the world, with no doubt absolutely, is the country of your bosses, ISRAEL. Israel is constantly threatening, invading, taking hostages and bombing other countries of the Middle east with the willing approval of USA.

As another poster says, " Nothing that Iran has done, including this reactor- is illegal". But yes, what Israel has done through the years in the middle east is against the peace of that region and illegal, that is why the UN has issued more than 30 resolutions condemning the criminal behavior of Israel against its neighbours.

For heaven's sake. Both Israel and Pakistan (not to mention the US) have exhibited worse behavior than Iran. Why not let that country alone and try to bring these intelligent and well meaning Iranians into the world community?The US-Israel policy is quite immoral. It is only sustained by the force of arms.

Having enough fissile material in a bunker somewhere is not sufficient: years of effort are required to build a miniaturized weapon that can be fitted on a missile.

So all these reports that Iran is months, weeks, days away from that goal are nonsense.

Israel and its erstwhile Saudi Arabian ally are working frantically to undermine the resolution of the nuclear issues surrounding Iran's legal pursuit of its nuclear development rights under international law.

Flinging the anti-Semitism charge, a desperate tactic by the losers who want yet another war.

No one is afraid of this moldy, old tactic any more, and it's actually intended not so much to intimidate people like Mr,. Vick but to scare American Jews into believing that they are surrounded by would-be Nazis.

@NotaNeocon "Known agents of Mossad" (!!!!!) Wow. Time's readership has really gone downhill. Phew. Tell me, how did you get the Mossad spy list? I mean don't they normally try to keep those things secret? But, somehow you got hold of it, and you looked inside and sure enough, you are saying, there was David Albright's name and to the right ".... Mossad agent abroad" -- excellent spycraft NotaBacon -- very sharp work.

As we've seen, the problem isn't "walking in" (with Iran that might be debatable), it's staying there to 'fulfill the mission'. That hasn't happened, on any appreciable scale, since great-grandpappy''s go-round in WW2. So much for all that power.

But, hey, back then America had a positive attitude and didn't feel the need to prove they were "the meanest Mo****-Fu****s in the valley". Or to be the best Mo****-Fu****s at all.

@arvay Actually, signatories to the IAEA, to which Iran is a signatory (Israel is not a signatory--joining is voluntary--it earns you uranium nuclear technology assistance), are prohibited from using their nuclear program in a manner that can be used for nuclear weapons. However, once a country voluntarily signs up to the IAEA, the requirements of the IAEA become binding to signatory members under international law. Iran has violated this legally binding requirement, under international law, six ways from Sunday. Also, threatening to attack member states of the UN offensively, when not directly and imminently threatened, is a violation of the UN charter, another serious violation of international law. Conversely, pre-emptive strikes when threatened directly and overtly are legally sanctioned under international law. Arvay, I suspect you do not care about actual international law.

At the worst, Iran has built a facility or two without first notifying the IAEA, scarcely grounds for the illegal acts of sabotage and assassinations launched against it by the US and Israel.

Also, Iran has not threatened to attack anyone, as both the US and Israel have, over and over (on the table, endlessly). Iran has said that Israel should never have been inserted in the region, and will no be there forever. As have millions and millions of people on the globe. This is not an attack, it is an opinion.

Yes, many Jews were involved in the revolution and subsequent Soviet state, not surprising, given the ethnocentricity of their religion and persecution and segregation by the Russian empire.

Some of these officials took the opportunity for vengeance, and some people were seemingly picked for certain roles because of their ethnic background. Felix Dzerzhinsky, head of the original secret police --was a Polish nobleman -- someone who was likely not to have a soft spot for Russians, And he killed lots of them.

In America, where Jews are not persecuted, they are assimilating faster than they are born -- a trend that alarms the Zionists. My country makes a lot of mistakes, but we assimilate people well, a good thing.

"Meanwhile, it is today China who will end up on top, not the European white man. "

I start with this quote from the end of your posting, because it clearly illustrates your antiquated, racist beliefs. As such, you're a typical Zionist, a believer in the superiority of those you think of as your own "people."

Likewise "People like to be ruled by their own." Spoken like a true supporter of apartheid or an American southern sheriff in the 1950s.

The monstrous things done to the Jews of Europe do not justify taking land from other people and inserting a fake nation among them.

And your denial of Palestinian aspirations -- the same aspirations you award, in your blinding arrogance -- to all the other "peoples" of the earth -- underlines your racism and hypocrisy.

Your Marxist starw-man is pathetic and borderline comical. "The commies are coming!

@arvay@Frankie_C Arvay, yes, I like Israel. I believe that the Jews have the right to self-determination and that life was hell for them in both Christian and Arab lands for 1,000 years or more. I believe the attitude of the winners in WWI in favor of national self-determination was correct. Not only for the Jews, but for the Arabs, for Eastern Europeans and, as should have been the case, for the Kurds, Basque and more. People like to be ruled by their own. Otherwise they get abused. And don't start up with the Palestinians. First, they do rule themselves today. Second, they had half a dozen bites at the apple and chose to kill the Jews each time, instead. Third, they are not a separate people from Arabs...never were. Just another precinct of where Arabs lived. By invading others. This is why Assyrians, Berbers and Copts are all endangered peoples/cultures...in their own lands. Arvay, I suspect you are an anti-Israel advocate. Your position, Arvay, typically arises from an attempt by the left to put the square peg of Israel into the round hole of European colonialism in order to refashion the old worker-capitalist Marxism into a new white-brown or North-South model. It's all a farce. Marxism was quite happy killing off 30 million in the former Soviet Union and 70 million in China and 5 million in IndoChina...with all of its trendy Western sympathizers knowingly turning a blind eye. Meanwhile, it is today China who will end up on top, not the European white man. India is not doing too badly, either, now that they placed Neiru-nomics into the trash. Arvay, you only look like a grotesque caricature by your Iran apologist comments. Iran's position on this is quite clear.